Molybdenum is stable in the air at room temperature. When the temperature is 400℃, slight oxidation occurs; when the temperature is higher than 600℃, the metal rapidly oxidizes to molybdenum trioxide; when the temperature is higher than 700℃, the water vapor strongly oxidizes molybdenum to molybdenum dioxide.
Molybdenum does not have any chemical reaction with hydrogen, but when heated in hydrogen, molybdenum can absorb some hydrogen to form a solid solution. Below 1500℃, molybdenum does not react with nitrogen, while above 1500℃, molybdenum reacts with nitrogen to form nitrides. Molybdenum reacts with carbon, hydrocarbons and carbon monoxide above 800℃ to form molybdenum carbide. When carbon dioxide is above 700℃, molybdenum is oxidized. In the presence of water, the halogen reacts with molybdenum at room temperature; in the absence of water, only fluorine reacts with molybdenum at room temperature to form volatile molybdenum fluoride (MOF6).
Boron interacts with molybdenum under heating. Sulphur vapor is higher than 440℃, while hydrogen sulfide needs to be higher than 800℃ to react with molybdenum to form molybdenum disulfide. Sulphur-containing gas can also oxidize molybdenum metal at 700-800℃. At temperatures above 1200℃, molybdenum interacts with silicon to form molybdenum disilicate (MoSi2) which is very stable in air as temperatures rise all the way up to 1500℃.
At room temperature, molybdenum is stable in hydrochloric acid and sulfuric acid. When heated to 800~1000℃, molybdenum is slightly dissolved. Molybdenum can be dissolved in nitric acid and aqua regia slowly at room temperature, and the dissolution rate is accelerated by heating. The metal molybdenum dissolves in hydrogen peroxide to form perhydroacids - H2Mo6 and H2Mo11. Molybdenum is stable in hydrofluoric acid but dissolves rapidly in a mixture of hydrofluoric acid and nitric acid. When the volume ratio of nitric acid: sulfuric acid: water =5:3:2, the mixture can be used as molybdenum dissolving agent.
